The present invention relates to an auto slurry deliver fine-tune system for chemical-mechanical-polishing process, more specifically, to an auto slurry deliver fine-tune system that is controlled by the turn-table current in chemical-mechanical-polishing process.
Chemical-mechanical-polishing (CMP) process is indicated as a global planarization process for deep sub-micron integrated circuits. One or several wafers, which have polishing thin film layers, are put on a polish pad of a CMP system and the polished thin film layers touches the surface of the polish pad for planarizing the wafers. As the wafers are polished on the polish pad, polishing slurry is dispersed on the polish pad for performing a chemical reaction upon the polished layers in the chemical-mechanical polishing process.
A top view of a polish pad 100 in a CMP system is shown in FIG. 1 and two polish heads 200 for fixing and pressing the wafers, which are polished for global planarization, are put on the polish pad. During the CMP process, the polish pad 100 is rotated with respect to its central point and the polish head 200 is rotated with respect to its central axis. The cross-section view of the polish pad 100 is shown in FIG. 3 and the polish head 200 is rotated with respect to the central axis 201. Still referring to FIG. 3, an injector 300 is placed above the polish pad 100 for dispersing polishing slurry thereon. Noted that the flow rate that the slurry is injected out the injector 300 and the position of the injector 300 are critical factors to effect the remove rate in CMP process.
Since the manufacture of integrated circuits must be cost down, the amount of the slurry used in CMP system should be reduced. In other words, how to use minimum slurry in a CMP process becomes an important issue of the manufacture of integrated circuits. Nevertheless, when the amount of the slurry in a CMP process is reduced, the remove rate of the wafers be polished in the CMP process will be decreased because the chemical reaction upon the wafers is not very active.
In a CMP system, there are four independent process parameters for determining the remove rate of wafers that are polished in the system. The parameters includes the pressure pressing on the polish head of the system, the pressure pressing on wafers in the system, the rotated rate of the polish pad of the system and the rotated rate of the polish head. Generally, as the four independent parameters are decided, the maximum remove rate of the wafers is simultaneously decided.
In a CMP process, how to reduce the flow rate of the slurry in order to increase or sustain the remove rate of the wafers becomes an important issue. In other words, as the four independent factors are determined, the issue is to find the optima value of the flow rate of the slurry and the optima distance X between the central axis of the polish head and the injector for dispersing the slurry on the polish pad.
The chemical-mechanical-polishing (CMP) process is a new technology in IC industry today. Sometimes it does not need so much slurry to polish the wafer, because the best slurry flow position is not known, especially at some special rotated rate, so some slurry is always wasted. It is needed a method of how to monitor the friction between pad and wafer in line and to use current feedback to make some judgement to fine tune the injector position and the flow rate of slurry.
The present invention provides an auto slurry deliver fine-tune system, comprising: a slurry flow system to vary a flow rate of the slurry in a CMP system and the distance between a slurry injector and a polish head of the CMP system; a current detect system to detect the current driving the turn-table of the CMP system; a judgement system to determine whether the current is minimum in order to determine that the flow rate and the distance are optima.
The present invention provides a method of a slurry deliver fine tune in a chemical mechanical polishing (CMP) system, comprising: varying a flow rate of the slurry in the CMP system and the distance between a slurry injector and a polish head of the CMP system; detecting the current driving the turn-table of the CMP system; determining whether the current is minimum; varying the flow rate and the distance until the current reaches to minimum; sustaining the flow rate and the distance for the optima flow of the slurry.
The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
FIG. 1 shows a top view of a conventional polishing pad, wherein polishing heads put on the pad;
FIG. 2 shows a block diagram of an auto slurry deliver fine-tune system for chemical-mechanical-polishing process in accordance with the present invention;
FIG. 3 shows a cross-section view of a conventional polishing pad, a polishing head put on the pad and a nozzle for injecting slurry put above the pad;
FIG. 4 shows the relationship of the turn-table current and the flow rate of the slurry in chemical-mechanical-polishing process that is controlled by the system in accordance with the present invention; and
FIG. 5 shows the relationship of the remove rate and the flow rate of the slurry in chemical-mechanical-polishing process that is controlled by the system, before and after the position of the slurry injector is modified, in accordance with the present invention.